For many years it has been known to aromatize a feed that is, above all, paraffinic, in the presence of platinum/chlorinated alumina type catalysts. More recently, this aromatization has been realized in the presence of catalysts containing a metal of Group VIII of the Periodic Table of the Elements supported on a zeolite, especially a zeolite-L, exchanged, preferably, at more than 90% by alkaline ions.
U.S. Pat. No. 4,104,320 in the name of the applicant describes such a catalyst. These catalysts have the advantage of being easily reactivable through hydrogen treatment.
French patent publication No. 2,484,401 in the name of the applicant describes a process for the dehydrocyclization of paraffins using two reactions, one of the reactors producing aromatic hydrocarbons, while the other is swept by hydrogen produced in the first reactor in order to reactivate the catalyst; thereafter, the reactors are commuted. Such a process allows lengthy operating without loss of selectivity of the catalyst. Nevertheless, after a considerable time clogging of the catalyst due to coke deposit occurs and the catalyst can no longer satisfy its role and must therefore be regenerated.
It is known to regenerate aromatization catalysts by burning coke in an atmosphere containing oxygen. This combustion is often preceded by a sweeping step with hydrogen or nitrogen. The catalyst is thereafter subjected to oxychlorination by heat treatment by mixtures of air and chlorine or, further, by chlorinated compounds such as CCl.sub.4 in the presence of air.
When this regeneration process is applied to the catalyst of the type formed of metal of Group VIII supported on zeolite, a large part of its selectivity is effectively restored. Nevertheless, it has never been possible to obtain exactly the values of the initial selectivity.